Multiple functions of the vesicular proton pump in nerve terminals

Synaptic vesicles are acidified by a proton pump (vATPase), which allows vesicular uptake of neurotransmitters. After vesicle exocytosis, continued operation of the vATPase would seem to serve no useful function. In this issue of Neuron, however, Zhang and colleagues show that continued pumping alkalinizes the cytoplasm, accelerating endocytosis.     

EphA4-dependent axon guidance is mediated by the RacGAP alpha2-chimaerin

Neuronal network formation in the developing nervous system is dependent on the accurate navigation of nerve cell axons and dendrites, which is controlled by attractive and repulsive guidance cues. Ephrins and their cognate Eph receptors mediate many repulsive axonal guidance decisions by intercellular interactions resulting in growth cone collapse and axon retraction of the Eph-presenting neuron. We show that the Rac-specific GTPase-activating protein alpha2-chimaerin binds activated EphA4 and mediates EphA4-triggered axonal growth cone collapse. alpha-Chimaerin mutant mice display a phenotype similar to that of EphA4 mutant mice, including aberrant midline axon guidance and defective spinal cord central pattern generator activity. Our results reveal an alpha-chimaerin-dependent signaling pathway downstream of EphA4, which is essential for axon guidance decisions and neuronal circuit formation in vivo.     

Association between TAS2R38 gene polymorphisms and colorectal cancer risk: a case-control study in two independent populations of Caucasian origin

Molecular sensing in the lingual mucosa and in the gastro-intestinal tract play a role in the detection of ingested harmful drugs and toxins. Therefore, genetic polymorphisms affecting the capability of initiating these responses may be critical for the subsequent efficiency of avoiding and/or eliminating possible threats to the organism. By using a tagging approach in the region of Taste Receptor 2R38 (TAS2R38) gene, we investigated all the common genetic variation of this gene region in relation to colorectal cancer risk with a case-control study in a German population (709 controls and 602 cases) and in a Czech population (623 controls and 601 cases). We found that there were no significant associations between individual SNPs of the TAS2R38 gene and colorectal cancer in the Czech or in the German population, nor in the joint analysis. However, when we analyzed the diplotypes and the phenotypes we found that the non-taster group had an increased risk of colorectal cancer in comparison to the taster group. This association was borderline significant in the Czech population, (OR = 1.28, 95% CI 0.99–1.67; P_value = 0.058) and statistically significant in the German population (OR = 1.36, 95% CI 1.06–1.75; P_value = 0.016) and in the joint analysis (OR = 1.34, 95% CI 1.12–1.61; P_value = 0.001). In conclusion, we found a suggestive association between the human bitter tasting phenotype and the risk of CRC in two different populations of Caucasian origin.     

Cellular localization and subcellular distribution of Unc-33-like protein 6, a brain-specific protein of the collapsin response mediator protein family that interacts with the neuronal glycine transporter 2

Unc-33-like protein (Ulip)6, a brain-specific phosphoprotein of the Ulip/collapsin response mediator protein family, was originally identified in our laboratory by yeast two-hybrid screening using the cytoplasmic N-terminal domain of the neuronal glycine transporter, glycine transporter (GlyT) 2, as a bait. Here, the interaction of Ulip6 with the N-terminal domain of GlyT2 was found to be specific for this member of the Ulip/collapsin response mediator protein family and to involve amino acids 135-184 of GlyT2. In pull-down assays and coimmunoprecipitation experiments with rat spinal cord extract, the presence of phosphatase inhibitors significantly enhanced binding of Ulip6 to GlyT2. Subcellular fractionation of spinal cord and retina homogenates at different developmental stages showed Ulip6 immunoreactivity to be associated with light vesicles that were distinct from GlyT2-containing and synaptic vesicles. Immunocytochemistry revealed punctate Ulip6 immunoreactivity in both somatic regions and processes of cultured spinal neurones; no colocalization with GlyT2 or other synaptic marker proteins was found. In retina, which expresses only GlyT1 but not GlyT2, Ulip6 was detected in the inner plexiform layer and along the somata and processes of selected bipolar, amacrine and ganglion cells. Our data support a model in which Ulip6 transiently interacts with GlyT2 in a phosphorylation-dependent manner.     

Effects of inhaled corticosteroids on sputum cell counts in stable chronic obstructive pulmonary disease: a systematic review and a meta-analysis

Background

Whether inhaled corticosteroids suppress airway inflammation in chronic obstructive pulmonary disease (COPD) remains controversial. We sought to determine the effects of inhaled corticosteroids on sputum indices of inflammation in stable COPD.

Methods

We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Databases for randomized, controlled clinical trials that used induced sputum to evaluate the effect of inhaled corticosteroids in stable COPD. For each chosen study, we calculated the mean differences in the concentrations of sputum cells before and after treatment in both intervention and control groups. These values were then converted into standardized mean differences to accommodate the differences in patient selection, clinical treatment, and biochemical procedures that were employed across original studies. If significant heterogeneity was present (p < 0.10), then a random effects model was used to pool the original data. In the absence of significant heterogeneity, a fixed effects model was used.

Results

We identified six original studies that met the inclusion criteria (N = 162 participants). In studies with higher cumulative dose (≥ 60 mg) or longer duration of therapy (≥ 6 weeks), inhaled corticosteroids were uniformly effective in reducing the total cell, neutrophil, and lymphocyte counts. In contrast, studies with lower cumulative dose (< 60 mg) or shorter duration of therapy (< 6 weeks) did not demonstrate a favorable effect of inhaled corticosteroids on these sputum indices.

Conclusions

Our study suggests that prolonged therapy with inhaled corticosteroids is effective in reducing airway inflammation in stable COPD.     

Behavioral effects of inhibition of cannabinoid metabolism: The amidase inhibitor AM374 enhances the suppression of lever pressing produced by exogenously administered anandamide

Biochemical investigations have identified putative enzymatic pathways for the synthesis and metabolism of endogenous cannabinoids. Anandamide amidase is an enzyme that metabolizes anandamide into arachadonic acid and ethanolamine. Using in vitro methods, various inhibitors of amidase have been identified. The present studies were undertaken to determine if the amidase inhibitor AM 374 could enhance the effects of intraperitoneal (IP) injections of anandamide. Three studies were conducted to investigate the effects of various drug treatments on fixed ratio 5 operant lever pressing for food reinforcement. In the first study, the effects of different doses of anandamide were assessed, and it was demonstrated that 5.0 and 10.0 mg/kg anandamide IP significantly suppressed lever pressing, while 2.5 mg/kg produced very little effect. The second study tested the effects of intraventricular (ICV) injections of AM 374, and it was observed that doses up to 10.0, 20.0 and 40 microg AM 374 had no significant effect upon lever pressing. The third study investigated the combined effect of AM374 with a low dose of anandamide. Rats received two drug injections: one ICV and one IP. Four different drug treatments were assessed: 1) ICV vehicle + IP vehicle, 2) ICV vehicle + 2.5 mg/kg anandamide IP, 3) ICV 20.0 microg AM 374 + IP vehicle, and 4) ICV 20 microg AM 374 + 2.5 mg/kg anandamide IP. Combined administration of AM 374 plus anandamide led to a significant decrease in lever pressing compared to either AM374 or anandamide administered alone. Observations of the animals treated with the combination of AM374 plus anandamide indicated that the drug combination resulted in motor slowing, which is consistent with the notion that stimulation of cannabinoid receptors produced a motor deficit that interfered with lever pressing. Although AM374 produced no effect on its own, this amidase inhibitor did enhance the behavioral effect of a low dose of anandamide. These results are consistent with the notion that AM 374 inhibited the enzymatic breakdown of exogenously injected anandamide. This type of procedure can be used to assess a variety of different compounds for their ability to inhibit cannabinoid metabolism.